Under hydrogenation conditions, when a hydrocarbon feedstock contacts with a catalyst, reactions that may occur include, such as, hydrogenation, hydrodesulfurization, hydrodenitrogenation, hydrodemetallization, hydrodearomatization, hydroisomerization, hydrodewaxing, hydrocracking and mild hydrocracking and so on. In this case, the catalyst is generally composed of carrier-supported VIB group and VIII group metal components. The hydrogenation-active metal components are usually selected from Co or Ni—Mo or Co or Ni—W, and the carrier is usually selected from alumina, silica-alumina and their modifiers. These catalysts can be prepared by steps of impregnating the carrier with an aqueous solution containing said metal compounds, then drying and calcining the thus obtained, and the like; or by co-precipitating the carrier together with VIII Group metal components and VIB Group metal components. Generally speaking, for a reaction process wherein desulfurization is the main reaction, the hydrogenation-active metal component of the catalyst is preferably a Co(Ni)—Mo combination; and for a reaction process wherein hydrogenation is the main reaction, such as an aromatic-saturation reaction, the metal component is preferably a Ni—W combination.
Under certain conditions, the Mo-modified NiW/Al2O3 (The hydrodesulfurizing performance of the Mo-modified NiW/Al2O3 catalyst for thiophene, Proceedings of China 10th Catalysis Meeting, 2000, p 491) or the W-modified NiMo/Al2O3 (Modification of the alumina-supported Mo-based hydrodesulfurization catalysts by tungsten, Catalysis Letters 53 (1998), 193˜198) are all favorable for increasing the activity of alumina-carrier-supported catalysts.
CN1083476C discloses a hydrorefining catalyst for distillates and a method for producing the same. Said catalyst, comprising VIII Group and VIB Group metals as the active component, phosphor as the adjuvant, and alumina or siliceous alumina as the carrier, is characterized in that said catalyst comprises W, Mo, Ni as the active components, P as the co-catalytic component, and based on the weight of the catalyst, it contains 13˜25 wt % of WO3, 6˜14 wt % of MoO3, 2˜7 wt % of NiO and 1˜9 wt % of P2O5, with a pore volume of 0.22˜0.37 ml/g, and a specific surface area of 110˜170 m2/g. The method for producing the catalyst comprises: weighing alumina or siliceous alumina as the carrier; W, Mo and Ni as the active components, and P as the adjuvant component, formulating a co-immersing solution with these components, then heating the solution at 70˜120° C., repeatedly impregnating the carrier in said co-immersing solution, drying the impregnated carrier at 80˜150° C. for 8 hrs, then calcining it at 450˜550° C. for 2˜5 hrs to obtain the catalyst.
CN1098915C discloses a hydrorefining catalyst and a preparation method thereof. The catalyst comprises VIII Group and VIB Group metals as the active components, and boron as the adjuvant component, characterized in that, by weight percentage, the catalyst comprises 3˜10% of SiO2, 5˜10% of MoO3, 10˜25% of WO3, 2˜5% of NiO, and 2˜5% of B2O5. Said catalyst is prepared by impregnating a molded carrier once with a mixed solution containing the active components and the adjuvant component, then drying and calcining the thus obtained.
In addition, with the increasing demand for diesel oil across the world in recent years, it is required for the catalytic cracking process to produce diesel oil in a higher yield. The catalytic cracked diesel oil is characterized in high sulfur, nitrogen and aromatics contents, low cetane number, poor store stability and large volume of toxic gases generated from the combustion. Hydrotreation of diesel oil in the presence of a hydrotreating catalyst can remove sulfur and nitrogen, and decrease aromatic content, resulting in diesel oil with an improved quality.
CN1054150C discloses a conversion catalyst for hydrogenating diesel oil. The catalyst comprises a carrier consisting of alumina, an amorphous silica-alumina and a molecular sieve, and hydrogenation active metals supported on the carrier. The catalyst contains 10˜30 wt % of WO3, 2˜15 wt % of NiO, 5˜45 wt % of the molecular sieve, 30˜70 wt % of alumina, and 5˜25% of the amorphous silica-alumina. Said molecular sieve is a Y-molecular sieve having an infrared total acidity of 0.5˜1 mmole/g and a lattice constant of 2.436˜2.444 nm. Said alumina is a micropore alumina with a pore volume of 0.8˜1.1 ml/g and a surface area of 230˜400 m2/g.
CN1184843A discloses a conversion catalyst for hydrogenating diesel oil, comprising: 40˜80 wt % of alumina, 0˜20 wt % of an amorphous silica-alumina, and 5˜30 wt % of a molecular sieve which is a Y-molecular sieve having a pore volume of 0.40˜0.52 ml/g, a specific surface area of 750˜900 m2/g, a lattice constant of 2.420˜2.500 and a silica-alumina ratio of 7˜15, and 10˜30 wt % of a VIB group metal and 2˜15 wt % of a VIII group-metal oxide.
U.S. Pat. No. 5,030,780 discloses a saturation process for aromatic compounds in the presence of a catalyst containing hydrogenation metals supported on a carrier. Said carrier contains a zeolite and a porous heat-resistant inorganic oxide, especially a heat-resistant inorganic oxide having silica-alumina dispersed in an alumina matrix. Said zeolite includes various crystallo-silica-alumina zeolites, naturally occurred or synthesized, such as faujasite, mordenite, erionite zeolite, Y-zeolite, X-zeolite, L-zeolite, Ω-zeolite, ZSM-4 zeolite, Beta-zeolite and the like.
CN1400284A discloses a hydrotreating catalyst for diesel oil, which contains a carrier and molybdenum and/or tungsten and nickel and/or cobalt supported thereon, characterized in that said carrier is composed of alumina and a zeolite, with a weight-ratio of alumina to zeolite in the range of from 90:10 to 50:50. Said alumina is composed of a micropore alumina and a macropore alumina in a weight-ratio in the range of from 75:25 to 50:50, wherein the micropore alumina is one wherein the volume of the pores of less than 80 Angstrom in diameter accounts for 95% or more of the total pore volume, and the macropore alumina is one wherein the volume of the pore having a diameter of 60˜600 Angstrom accounts for 70% or more of the total pore volume.
In comparison with a conventional hydrogenation catalyst comprising two metal components, the hydrogenation catalyst comprising three metal components according to the prior art shows a mildly rather than sufficiently improved activity. The catalyst does not sufficiently meet the increasing needs for hydrogenating hydrocarbon oil.